Damping Mechanical Energy Distortion of STAX and other phones with SORBOTHANE and other materials.

  1. edstrelow Contributor
    (Edit October 13, 2015 This thread has changed considerably since i started it with the intention of showing how the sound of Stax phones could be improved by using sorbothane on various portions of the earcups. Several other Headfiers have joined in to discuss the use of sorbothane and even some other materials to achieve these improvements on Stax and various other phones. This is all to the good in my opinion because it has gradually become evident that there is a problem of undamped mechanical resonance in many, if not all headphones. The more phones which are studied the more we will come to understand the nature of the underlying issues of mechanical resonance. It is clear that this is no longer simply an issue for Stax or even electrostatic phones.

    My efforts and those of others to come up with damping strategies with Stax phones are found in the earlier posts. Whenever I have modified my methods, I have edited the posts for those phones, including the Stax Lambdas, SRX III pro, Sigma/pro, SR007 and SR003 so what is there should represent my latest take.

    I am trying to get another thread started to explain this problem. It is taking me a while to get this together, although there are snippets of explanations scattered throughout this thread and the previous thread dealing with the SR007 )

    I have been toying with a write-up of my efforts to damp the vibrations in the earcups of various Staxen by sorbothane, something I have been playing with for almost 1/1/2 years. I realized that it was going to take a long posting to cover the 007A, 003, SRX3 Pro, Sigma Pro, Sigma/404 , Lambda LNS and Lambda 404 and that I was just not going to get it done. That plus the fact that I am still experimenting and have by no means fully explored this phenomenon to my satisfaction. However, I am reasonably happy with what I have done with the Lambdas and as these are probably the most common Staxen I thought it would be worth reporting these first.

    EDIT 5/28/15 - When I started this work I did not have much more to go on than that I had found that under some circumstances the application of sorbothane to the earcups or other parts of some headphones could make an almost remarkable change in their sound. Now I realize that as important as that may be, more significant is the fact that doing anything to the body of the phones could markedly change their sound. I now believe this means that there is a large amount of mechanical energy floating around most phones, which is insufficiently damped and which is messing up the sound of even the best phones. Even more remarkable is that this phenomenon has either not been observed before or been ignored by even the top headphone makers. I will develop this argument at a later time, although portions of it are scattered throughout this thread. I am keeping the current thread for discussions of what may be the more effective types of sorb mods for the various Stax phones I own.

    I got started on this issue when I noticed that the arc assembly of the 007A appeared to impact the sound of these phones. http://www.head-fi.org/t/671314/stax-sr007-resonance-problems I will grant that the first reaction of anyone who looked at this posting was very likely WTF? It is odd to claim that the headband has an impact on sound. But that's what I heard. I put together a simple damping mechanism using sorbethane and a plastic clamp, played with it, liked what it did to the sound and left it alone for many months. (EDIT: so far I have only heard this on the 007, but cucera has recently reported damping the headband of the 4070, which looks like it has much the same kind of band arrangement as the 007, i.e it screws directly to the earcups. Other Stax headbands, have at least one other segment separating the headband from the earcups and that, I used to believe, makes a big difference. Now it is more evident that it is easy for vibrations to travel across most headbands. Companies including B&W and Audioquest are specifically working on this problem.

    After a while it dawned on me that even though the arc assembly may have been vibrating during the playing of music, the real problem had to be where the vibrations were coming from, presumably the earcups themselves since that was where the energy originated. I.e. there was energy floating around the earcups which was making it to the 007A arc assembly because of the way the earcups were tightly screwed to the arcs. If so, was there a similar issue with other Stax headphones and how could you find out?

    After an even greater time I started playing around first with a Sigma Pro by putting a strip of sorbethane across the bottom front of the earcups. It made the sound awful. The bass could only be described as flatulent i.e a bass fart. There may have been some increased clarity in the upper and mid frequencies but the awful bass squelched this experiment. However it did show that something was going on in the cups and I did eventually come up with a reasonable fix for the Sigmas. But I am still playing with it so I don't want to discuss it first.

    The Lambdas were a lot easier. There is room on the baffle board that holds the transducer to attach strips of sorbethane around the drivers. I used self-stick sorbethane about 1/8 inch thick. (EDIT I am now using 1/4 inch 70 duro sorbothane, cut into small segments with no dimension longer than 3/4" to 1. I am also playing with 1/2 " sorb but this is very difficult to locate on many phones, but is even better. The 1/8 inch is good but the 1/4" is better, and the small segments appear better than the longer segments noted in the original pictures.You can buy this stuff on ebay for a few bucks and it comes in various thickness down to 1 mm, with or without self-stick. It took about 10 minutes to install this on the Lambda LNS and 404s and because it's out of sight you would never know it's there. It may add an ounce or so weight to each cup.


    So what does it do to the sound? Makes it tighter, cleaner, gets rid of some fuzziness and brings out sonic detail including harmonics. It's hard to do a before and after comparison with the Lambdas because of the time it takes to install the sorbethane but I was able to do this with the Sigmas because with these the sorbethane was simply stuck to the outside of the cups ( after I got an arrangement that I thought sounded good) and could be just peeled off. With both Sigmas, upon ripping off the sorbothane suddenly there was a jump in sound level, in which an odd ambience suddenly appeared. It wasn't unpleasant but it probably wasn't music either. It adds a fair bit to the volume though and probably ends up masking the sound coming from the drivers. This, I think is resonance which is getting damped by the sorbothane resulting in a lower overall signal. With all of the Stax I have tried with sorbothane, I find I am turning up the volume more. (but enjoying what I hear more too)

    So what have I got here? A possible tweak with Stax phones. It could work with others but I don't have anything else. I would be especially curious to know if dynamic phones are affected this way. And as I stated in the beginning, these are merely first efforts. There are obviously a lot of parameters to play around with such as the location of the damping material, how much to use, its thickness, how it is fastened (I am still working on clamps so that the pressure can be adjusted) and whether there might be other materials which could work better. Sorbothane also comes with different levels of stiffness (duro) so presumably this is a factor too.

    A number of people have been reluctant to open them up to put sorb inside. However there is little or no other place on the earcups to put any significant amount of sorbothane. On other phones, you can place it outside but the Lambdas have almost no solid surface to do this, except the baffle. The lambdas are not that hard to open. For a start you don't need to remove the earpads, such peel them back a bit and unscrew the corner screws.

    The baffle may be somewhat stuck. Stax does not glue them as should be obvious from the use of 4 screws to hold the baffle in place. However the baffle can feel stuck, possibly because glue from the earpads gets in to the space. However, a bit of careful prying will get the baffle out.


    Lift the baffle a few millimeters all around and then lift it up along with the section where the cord enters the earcup and voila you are ready to go.
    Last edited: Apr 28, 2017
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  2. edstrelow Contributor

    This shot shows my latest sorbothane follies with the SRXIII Pro.  All I have done here is put some 1/8 inch self-stick strips of 50 duro sorbothane on the metal housing around the ear cups. ("duro" is a measurement of hardness, 0 being the softest and 100 being the hardest) The right side is the modded unit and the left shows an unmodded SRXIII (unfortunately not  a pro.)   If the Lambdas are the most common Stax, the SRXIII pro is probably the rarest. I recall reading that there may be as few as 1,000 made.  Mine is a "frankenphone" a SRXII with pro drivers from the Gamma pro.  I believe it was modded in England but I bought it from a Headfier in Italy.
    There are  a lot of low bias SRXIII's around and they were at one time quite popular. They have a very smooth middle and were often used as monitor phones.  However the bass rolls off fairly quickly and because they rest on the ear they are not as comfortable as most circumaural designs.  The pro largely corrects the bass problem of the low bias model and adds more dynamics.  Compared to many newer pro phones they have a slightly raspy sound possibly related to what sounds like a small peak around 2kHz or thereabouts.
    The sorbothane cleans up the sound overall, getting rid of much of the raspiness and just letting everything else like timbre, dynamics  and rhythm come through better. Last night I was  tripping with  these phones, on just about everything, even opera where I normally prefer Sigmas.  The voices were powerful, clean and smooth.  Listening to von Karajan's old Otello I felt I was hearing the recording properly for the first time, so much clean detail and ambience came through. With other music such as rock I was again struck by how good the voices were and how well localized the singers and instruments were.  The soundstage was wide and precise.
    As with the Lambdas I reported on above, I am happy with this set-up,  It is simple to do and cosmetic in appearance.  In fact I really should try this on the SR007A's. In any case I will try 1/4" sorbothane on the SRXIII's after I get some delivered.
    As tweaks go, Sorbothane is easy to work with at least on these phones. It's a few bucks to buy so you've got little to lose if you don't like what it does. It's not like spending $5K for the latest tube amp and the sonic improvement can be substantial.
    As I said before these are experiments and I don't believe I have figured out what the best approach may be on any of these phones.  I still like the idea of clamps to adjust the sorbothane pressure, but so far I have only tried that with the 007A and Sigmas and am still trying to find or make  a good clamp.
    Nevertheless I don't see myself going back to naked headphones (i.e.phones without damping.)
  3. Tachikoma
    Why would sorbothane dampen mechanical resonances any better than the coupling between the headphone to the ears/head though? I think adding sorbothane would just add a bit more mass to the cups and shift the resonant frequency, if it is a mechanical resonance you're hearing.
  4. edstrelow Contributor
    The fact that I am hearing a significant difference in sound of Staxen with the addition a of fairly small amount of sorbothane ( and with the 003 which I haven't reported yet I use a miniscule amount) tells me that the "coupling between the headphone to the ears/head" does not dampen all the resonance that one hears.  I agree that Sorbothane  does add mass and that is a factor in what is going on.  However it is a fairly light substance so I suspect this is  not as big a factor as its elastic properties.  To the extent I have tried to figure out the science here, it seems to get into a lot of issues about materials or mechanical engineering which I have little grasp of. but which look sufficiently complicated that they will not lead to simple answers.
    The use of Sorbothane has been going on for decades in all sorts of areas including audio and you are probably familiar with the various footers that have been sold to reduce vibration. I am not aware of it being used with headphones although yesterday  I saw in an ad from an Amazon seller that some people are adding it to the inside of speakers.   That seems similar to what I am doing.
    Many of us go to great efforts to get rid of resonance problems in speakers. Speakers are generally heavy and rigid.  Some people use spikes to make  a firm connection with the floor. I see nothing like this with headphones.   Presumably the coupling you describe does something but just not enough. Obviously we are not able to add much mass or spikes to headphones. .  Maybe someone can come up with a better coupling, but so far what  I am hearing suggests that significant problems remain with current designs.
  5. cucera
    OK you made me curious and I have ordered the self adhesive sorbotane for my SR-X pro.
  6. edstrelow Contributor
    I see that you have "Stax SR-X MK3 pro with Omega pads."  You mean like as in the original Stax Omega?  I would not have thought that they would fit and if they did they must be expensive.  Certainly the regular SRX pad has issues,  they are uncomfortable and don't provide  a good seal. I look forward to your observations on the SRX.  You might try playing with some other phones too.
  7. Tachikoma
    Pretty sure he meant O2 pads. They do fit, but the SR-X+O2 combo can be a bit weird sounding at times. I blame the small opening on the SR-X driver, which probably causes reflections if you use a circumaural pad with them.
    Get some bungee cord and tighten the headphones more securely to your head :D
  8. cucera
    Yes Tachikoma is right regarding the O2 pads and Iagree somewhat with his assesment of the SR-X mod. I forgot to change my gear list, but I went back to the Stock pads. The 02 pads were verry comfortable but the bass and highs were a bit off.

    The SR-X MK3 pro is right now my second favourit Stax (009 and 007 MK1 share nr1 the first for classical the second for rock).
  9. edstrelow Contributor
    Some years back when I first went back to the SRXIII I bought a low bias model that came with a beat-up looking foam earpad.  I  bought the leatherette replacement  but found that it didn't sound as good as the foam. Unfortunately by then the foam has ripped part in the process of removing it.  The openings of the leatherette replacement pads are also a bit too small and cover part of the opening to the driver. The comfort and seal are not good either.  I am thinking of putting some foam under the pads to give them a bit more body to improve both comfort and seal.
    When I got the SRXIII pro a couple of years ago, I was delighted with the balanced sound even though it had a bit of roughness compared to later model Staxen.
    I think it would be amazing if one could get drivers for this phone rebuilt with the newer thinner membranes.  I contacted Stax Japan about this  some time back and they replied that they would only consider this if they had orders for several hundred.
  10. edstrelow Contributor
    I put some self-stick sorbothane strips around the outside of the 007A.  I am still playing with the various bits of sorb  I am using as I have sorb clamped on the headband arcs, as well as clamped on the upper part of the earcups.  The self-stick does not seem to give a good stick at first but seems to hold better after a day or so, if it hasn't fallen off in the meantime. With clamps you don't have to worry so much about adhesion and I seem to be able to tweak the sound by adjusting the pressure.
  11. cucera
    OK I can confirm that it helps a lot with the SR-X pro. The bass gets deeper with less loss in SPL and the whole sound gets more relaxed! Thanks Edstrelow.
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  12. edstrelow Contributor

    Glad you like it. I am pretty happy with the sorb fixes I have used with the SRXIII, my two Lambdas and the SR003. I am still playing with the 007As and Sigmas. I am getting some good sound from these latter phones but also some bass anomalies. I am enjoying the new sound of the other phones so much that I am not spending the time to figure out the 007A and the Sigmas.
  13. cucera
    Could you please post about the 003 mod?
  14. edstrelow Contributor
    This is my sorbothane fix for the SR003.  It uses 1mm thick sorb.  I just pulled the ear-piece out of its holder and stuck on the sorb, no glueing was needed and then I just snapped the unit back together.
    I had originally used more sorb, so as to cover the entire back, except for the vent.  But I found that while the treble/midrange sounded good,  the bass became loud and distorted.  I have also noticed this at one time with my Sigmas.   So based on my guess that somewhere between the original amount of sorb and none, there would be sweet spot, I just kept cutting off sorb until I got  clarity across the audio spectrum.   I think it sounds very good.  Again, I am not saying that this is the ideal, merely something that I have found to work that is simple and cosmetic. 
    EDIT 5/28/2015  I recently made  a minor change to this mod which gave a big, and favorable change in sound.  It consisted of simply cutting the sorb piece in two and then replacing it.  This has the effect of making the mid range and treble more prominent and reducing much of the "mid-bassiness" of these phones.  Again, I don't know if this is the ideal  damping for these phones, just something which seems to work well.
    The last 2 photos show where I am in exploring the use of sorb with Sigmas and the 007A.  These are not necessarily recommended fixes, but rather works in progress.
    With the Sigma/404 I had originally opened up the case to see about putting sorb on the back of the plate that holds the driver, as I had done with the Lambdas.  There  didn't seem to be enough room on the Sigma, since the case cuts down on the free room.   So I  tried just  a 1/8 in thick strip on the bottom of the outer case. Initially, this gave real bad bass, just as I noted for the SR003 above.  However, subsequently I realized that the strip was not very secure and if it was firmly attached the sound improved across the spectrum.  I did this by getting some self-stick sorbothane.
    You can also  see that I am toying with metal clamps to hold down the sorb. The advantages of clamping are several.  You don't need to use  glue and you can to some extent tune the sound by adjusting the tightness of the clamps.  In general, tightening the clamp gives more treble and the less bass. These metal clamps are not however very secure or cosmetic so I am still looking.
    With the 007A, you can see my original clamps on the headband arc.  They work fine sonically  but the extra bits of sorb seems to make the sound even better.  I have added clamped sorb on the upper tab of the earcup and have added a strip of sorb around the earcup, just as I did with the SRXIII Pro.   Overall, the sound is very good but I get an occasional boom on very deep bass and  I would like to try for a better midrange.  Also the metal clamps are not very secure. So I want to do more experimenting. 
  15. edstrelow Contributor
    I have determined that dynamic headphones may also need sorbothane damping.  Since I only had electrostatics in the house it wasn't clear to me if what I am observing was just a problem with stats.  However one of my daughters brought a set of dynamic gaming phones with her while she  took a break from college over the holidays.  Putting a 1" square 1/8" thick sorb on the back of these phones gave essentially the same effect as I had noted with several stats. some grungy, harsh distortion disappeared giving cleaner just about everything, spatial separation, timbre and the like. So it I would guess that most phones need damping.  I say this based on my analysis above, that headphones can not be damped as effectively as speakers because of their lightness and lack of something solid to fasten them to.
    I am not making much progress in finding a good damping regime for Sigmas and the 007A.   I don't have a lot of free time and frankly I am enjoying my damped Lambdas and SRXIII pro so much that I feel little incentive to work on those other phones. Which is odd because for a few years previously  I preferred the Sigma/404 and 007A to all others. Hopefully I can figure out something in time for the Canjam in Orange county California in the next few months.  If not I'll just show up with what I have and some sheets of self-stick sorbothane.

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